Treatment of hydrocarbon oils



Patented Dec. 21, 1937 PATENT OFFICE TREATMENT OF HYDROCARBON OILS Wayne L. Benedict, Chicago, 111., Universal Oil Products Company,

assignor to Chicago, IIL,

a corporation of Delaware No Drawing. Application May 23, 1938,

4 Serial No. 81,509

I Claims.

This invention relates particularly to the treatment of the lower boiling naphthas and gasolines produced in the straight run distillation and in the cracking of petroleum though it may also be applied to analogous low boiling distillates produced in the primary distillation of any naturally occurring hydrocarbonaceous materials or in the secondary distillation of their primary tars.

More specifically, the invention is concerned with improved methods for treating crude primary gasoline boiling range distillates to render them suificiently stable and pleasing in appearance and odor from a sales standpoint.

Primary naphthas and gasolines quite uniformly require some type of chemical treatment to eliminate objectionable constituents of a colored, odorous or' gummy character. Color has been variously attributed to suspended asphaltic and resinous materials, oxidized hydrocarbons, nitrogen compounds and even to some pure hydrocarbons. The objectionable odors are principally due to sulfur compounds of which the chief offenders are the sulfur alcohols or mercaptans. The gummy or potential gum-forming constituents are heavy hydrocarbon polymers or highly unsaturated hydrocarbons such as conjugated dioleflns respectively.

It is the object of chemical treatments to remove suflicient quantities of the groups of impurities mentioned above until they are reduced to a point corresponding to a finished gasoline. A conventional treatment consists in the primary use of sulfuric acid of graded strength to remove unsaturates and, to some extent sulfur and nitrogen compounds, followed by neutralizing and redistilling to leave high boiling polymers and sludge reaction products as a residue. The application of so-called sweetening agents may be practiced either before or after the distillation following acid treatment or may be applied to distillates which have not received any acid treatment. These sweetening reagents apparently transform the foul smelling mercaptans into the relatively odorless and stable dialkyl disulfldes by chemical reactions involving oxidations with the removal of the mercaptan hydrogen and the condensation of the residual radicals.

A conventional sweetening treatment involves the use of sodium plumbite solutions followed by the addition of minimum amounts of sulfur to precipitate lead from the initially formed lead mercaptides and form the desired organic disul fldes. Owing to the numerous operating difflculties attending the use of plumbite, such as the tendency to emulsion formation and the danger of having to use too much sulfur to break the lead from solution, numerous other sweetening treatments have been proposed and some have attained commercial importance. The use of hypochlorites has been found applicable to certain distillates, principally those of. a straight run character and another developmeht has involved the use of copper compounds and it is with improvements in this last named type of sweetening process that the present invention is concerned.

In one specific embodiment, the present invention comprises the treatment of coppersweetened hydrocarbon oils for the removal of color and undesirable dissolved constituents by percolating said hydrocarbon oils through beds of granular solid contact materials comprising as their active constituent sulfides of heavy metals above hydrogen in the electrochemical series.

Owing to the relatively small percentages of compounds involved in the sweetening reactions, the course of copper-sweetening from the chemical standpoint is not entirely certain. In such sweetening processes cupric chloride as such has given good results and also mixtures of copper salts, for example, copper sulfate, and chlorides of the alkali and alkaline earth metals and ammonium. When gasolines are sweetened by percolation through these salt mixtures advantages are gained in making composites containing in addition to the active salts earthy or clay-like materials such as fullers earth. In such sweetening processes a large number of copper compounds may be employed either in a dry state or in solution and while in some cases there may be some actual removal of sulfur by combination with copper, there may in other cases be merely the formation of copper mercaptides or a true oxidizing action depending upon the character of the copper salt employed. It is therefore not possible to state exactly what reaction products are present in a copper-sweetened gasoline such as, for example, a cracked gasoline, to cause an increase in color in the treated product, but it has been quite generally observed that this increase in color occurs. There are some indications that it may be due to copper mercaptides and that it may be due in part to oxidized compounds depending upon the copper compounds employed and the conditions of treatment, however, it has been found that the color of copper-sweetened gasolines is practically always materially reduced by the subsequent use chromium, iron, cadmium, cobalt, nickel, tin, lead,

etc., which have been given in diminishing order of their electro-positiveness. The reasons for the refining action of these sulfides and their efilciency in removing the objectionable by-products from copper-sweetened distillates are not entirely understood but have been uniformly observed. When dealing with different gasoline stocks which have been sweetened by different copper compounds and under different methods of operation some of the sulfides enumerated may act with greater emciency than others so that they cannot be placed on an .exactly equivalent basis even though they may be used alternatively. The sulfides of zinc and iron have been found applicable in the majority of instances.

The sulfides employed may be produced by precipitation or other methods or may be the naturally occurring minerals such as, for example, in the case of iron, the commonly known pyrites and pyrrhotite minerals and in the case of zinc the mineral sphalerite. These metal sulfides may be mixed with or distributed over the surface of relatively inert spacing materials or carriers such as fullers earth, bentonite clays, ground pumice,

etc. in order to give better distribution and a greater surface of contact. Sulfides may be deposited upon such inert carriers by allowing them first to absorb a soluble salt such as ferric chloride from aqueous solution, the absorbed salt being then converted into the hydroxide by ammonia treatment and further converted into a mixture of sulfides by treatment with hydrogen sulfide.

The operation of the process is extremely simple and consists merely in passing the copper-sweetened gasoline through beds of granular material containing heavy metal sulfides at ordinary or slightly increased temperatures, using pressure it necessary to maintain substantially liquid phase conditions. It has been found that a small but 2,108,878 of heavy metal sulfides through which the sweetrather obscure character involving the conversion of dissolved reaction products, such as copper mercaptides into dialkyl disuifides on the one hand and copper compounds on the other. It is to be noted that copper is below hydrogen in the electrochemical series and there is a possibility that the initial reactions may involve the replacement of the copper in the reaction products by the metal in the sulfide used. Another possibility is that various compounds of copper containing sulfur, nitrogen or oxygen may react with the metal sulfides to form copper sulfide and metal oxides or hydroxides with the concurrent production of hydrocarbons. There is a further possibility that the color in the copper-sweetened distillates may be traceable to minute amounts of some of the copper salts originally used for sweetening and in this case the metal sulfides may again react to precipitate copper sulfide and form a compound of a heavy metal.

The following examples are given to indicate the efilciency of the proposed supplementary treatment for copper sweetened gasolines though it is not intended to limit the scope of the invention in exact correspondence therewith.

. Example I A sour Mid-Continent-West Texas cracked gasoline was sweetened by percolation at ordinary temperatures through a contact mass comprising cupric sulfate and ammonium chloride mixed with fullers earth. The sweetened product had a sulfide which brought the color back to that of the original sour stock and increased the induction period and inhibitor susceptibility. Similar results were obtained with pyrrhotite or with iron sulfide precipitated on pumice according to the method previously described. A yield of 30,000 barrels per ton of treated product was obtained and the following table shows the results of the treatment, along with the properties of the original sour stock.

Induction period, min. Color 8 in txeatm t Sulfide tmatm at d g ssgb it Without was com.

inhibitor inhibitor Nnna Nflnll 9 155 385 Copper Non Red...-. 40 120 Copper Ferrouuulfide 9 145 345 definite amount of moisture is essential to the Example II maintenanceof the activity of the solid materials. Another sour md continent west Texas treated may be due to some extent to removal of mechanically entrained finely divided particles but is evidently due principally to reactions of a cracked gasoline was sweetened during passage through a reagent consisting of 25 parts by weight of copper sulfate pentahydrate, 25 parts by weight of ammonium chloride and parts by weight of 16-30 mesh fullers earth. The eiiluent passed directly from the treating chamber into a tower containing a mixture of zinc sulfide and pumice. Sampling indicated that the gasoline from the sweetening tower had a red color and that it contained dissolved copper compounds. The gasoline leaving the zinc sulfide tower gave no test for copper with ammonium sulfide and a mere tra'ce by a spectroscopic examination of the hydrochloric acid extract. The color of the final product was the same as the entering untreated sour gasoline and the following table indicates the changes in the induction period and inhibitor susceptibility, up to a yield of 3200 bbls. per'ton of sulfide.

By the term chloride of an alkali metal" is meant the chlorides or sodium, potassium as well as the alkaline earth metals calcium and magnesium, and the hypothetical metal ammonium.

I claim as my invention:

1. A process for removing copper compounds from copper-sweetened'hydrocarbon oils which comprises treating the copper-sweetened oil with a solid sulfide of a heavy metal above hydrogen in the eiectro-chemical series.

2. A process for removing copper compounds from copper-sweetened hydrocarbon oils which comprises percolating the copper-sweetened oil through a bed of granular solid material containing a substantially water-insoluble sulfide of a heavy metal above hydrogen in the electro-chemical series.

. 3. A process for removing copper compounds from copper-sweetened hydrocarbon oils which comprises treating the copper-sweetened oil with zinc sulfide in solid Iorm.

4. A process for removing copper compounds from copper-sweetened hydrocarbon oils which comprises treating the copper-sweetened oil with iron sulfide in solid form.

5. A process for removing copper compounds from copper-sweetened hydrocarbon oils which comprises percolating the copper-sweetened oil through a bed of granular solid material containing zinc sulfide.

6. A process for removing copper compounds from copper-sweetened hydrocarbon oils which comprises percolating the copper-sweetened oil through a bed of granular solid material containing iron sulfide.

7. A process for removing copper compounds from copper-sweetened hydrocarbon oils which comprises treating the copper-sweetened oil in the presence of a relatively small amount or moisture with a solid sulfide of a heavy metal above hydrogen in the electro-chemlcal series.

WAYNE L. BENEDICT. 

